Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Reexamination Certificate
2004-01-20
2004-11-30
Riley, Shawn (Department: 2838)
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
C361S093800
Reexamination Certificate
active
06826028
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to buck converters, such as multi-phase buck converters for use in low voltage/high-current applications.
BACKGROUND INFORMATION
Various applications may provide a conventional DC-to-DC buck converter that accepts a DC input voltage and produces a lower DC output voltage to drive at least one circuit component. Buck converters are typically used in low voltage applications requiring high amounts of load current (e.g., 30 amps or more). Typically, as shown in
FIG. 19
, a single phase buck converter
1900
includes a high-side switch
1905
, a low-side switch
1910
connected to the high-side switch at a switch node
1915
, an output inductor
1920
connected to the switch node
1915
, and an output capacitor
1925
connected to the output inductor
1920
.
In operation, the high-side and low-side switches
1905
,
1910
are controlled by a control circuit
1930
to produce a desired output voltage across a load
1935
. For this purpose, the high-side switch
1905
is initially switched on, while the low-side switch
1910
remains off. This causes a voltage drop across the output inductor
1920
of approximately (V
IN
−V
OUT
), which causes a current to build inside the output inductor
1920
. At a subsequent time, the high-side switch
1905
is switched off, and the low-side switch
1910
is switched on. Since the current within the inductor
1920
cannot change instantly, sourced through switch
1910
, the current continues to flow through the output inductor
1920
, thereby charging the output capacitor
1925
and causing the voltage (V
OUT
) across the output capacitor
1925
to rise.
In this manner, the high-side and the low-side switches
1905
,
1910
may be suitably switched at appropriate times, until the voltage (V
OUT
) across the output capacitor
1925
equals a desired output voltage, which is typically lower than the input voltage. Once the desired output voltage is reached, the high-side and the low-side switches
1905
,
1910
may be periodically controlled so that the output inductor
1920
provides an amount of current equal to the current demand of a load
1935
connected across the output capacitor
1925
. By providing no more and no less than the current demand of the load
1935
, the voltage (V
OUT
) across the output capacitor
1925
remains at least approximately constant at the desired output voltage.
It is also known to provide a multi-phase DC-to-DC buck converter
2000
including a plurality of interleaving output phases
2005
a
,
2005
b
,
2005
c
, . . . ,
2005
n
, as shown in FIG.
20
. As shown in
FIG. 20
, each of the output phases
2005
a
,
2005
b
,
2005
c
, . . . ,
2005
n
is assigned a respective switching arrangement, including a high-side switch, a low-side switch, and an output inductor. In operation, the control circuit
2010
periodically operates the output phases
2005
a
,
2005
b
,
2005
c
, . . . ,
2005
n
in a time-delayed sequence.
By operating the output phases
2005
a
,
2005
b
,
2005
c
, . . . ,
2005
n
in a phase-delayed sequence, the conventional multi-phase buck converter
2000
distributes current production across the multiple output phases
2005
a
,
2005
b
,
2005
c
, . . . ,
2005
n
, thereby distributing heat generation and reducing the requirements for the output capacitor
1925
, such that a smaller output capacitor
125
may be utilized.
However, since conventional multi-phase buck converters require a fixed number of point-to-point connections between the control circuit
2010
and the output phases
2005
a
,
2005
b
,
2005
c
, . . . ,
2005
n
, conventional multi-phase buck converters do not provide a robust architecture capable of easy expandability to include any number of desired phases.
Furthermore, conventional multi-phase buck converters do not optimally control the output voltage in response to a request for a lower desired output voltage or a decrease in current demand of the load
1935
. By not optimally controlling the output voltage, conventional multi-phase buck converters may produce unwanted voltage spikes, which may damage circuitry connected to the output of the buck converter.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a multi-phase buck converter that overcomes the disadvantageous of prior art buck converters described above. To achieve this object, the present invention provides a multi-phase buck converter for producing an output voltage to a load, the output voltage being produced from an input voltage in accordance with a desired voltage, the converter including an output capacitor, the output voltage being provided by the output capacitor; a plurality of output switch arrangements having respective output inductors coupled to the output capacitor, the switch arrangements being controllable to provide respective phase output currents to the output capacitor through the respective output inductors; a plurality of phase output arrangements respectively coupled to the output switch arrangements, the phase output arrangements being controllable to set the respective phase output currents supplied by the output switch arrangements; a phase control bus communicatively coupled to each of the phase output arrangements; and a phase control arrangement communicatively coupled to the phase control bus, the phase control arrangement being configured to control the phase output arrangements to set the respective phase output currents supplied by the output switch arrangements so that the output voltage approximates or is regulated to the desired voltage, in which the phase control arrangement and the phase output arrangements are provided as respective integrated circuits, and the phase control arrangement is configured to control the phase output arrangements via the phase control bus.
By separating the functions of the phase control arrangement and the phase output arrangements, an exemplary multi-phase buck converter according to the present invention contains no unused or redundant silicon, since the buck converter may include only those number of phase output arrangements required for a particular application. Thus, if a design engineer requires, for example, a three-phase buck converter for a particular application, the engineer may design the multi-phase buck converter to include only three phase output arrangements, each of which is assigned to a respective one of the three phase outputs. Furthermore, the phase control bus (e.g., a 5-wire analog bus) permits the multi-phase buck converter of the present invention to communicate with a potentially unlimited number of phase output arrangements, without requiring point-to-point electrical connections between the phase control arrangement and each of the phase output arrangements. In this manner, the multi-phase buck converter permits an efficient and easily scalable phase architecture.
In accordance with another exemplary embodiment of the present invention, the multi-phase buck converter is provided with a phase error detect arrangement configured to produce a phase error signal if a phase output arrangement is incapable of providing a phase output current to match the average inductor current of the phase output arrangements. In this manner, the phase control arrangement is provided with a signal for detecting a defective phase and, if appropriate, may deactivate the defective phase and/or enable a back-up phase output arrangement.
In accordance with yet another exemplary embodiment of the present invention, each of the output phase arrangements operates to switch off both the high-side and low-side switches in response to a request for a lower desired output voltage (V
DES
) or a decrease in current demand of the load. In this manner, the slew rate of the inductor is increased, which enhances the response time of the multi-phase buck converter of the present invention and prevents disadvantageous negative currents from flowing through the output inductor and possibly damaging the power supply.
In accordance with still another exemplary embodiment o
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